Vent for liquid drainage system

ABSTRACT

A vent for a liquid drainage system having a drainage lumen, including an air chamber, a one-way valve connected to the chamber, and a passageway connected between the chamber and drainage lumen. The valve opens to permit the passage of air into the drainage lumen, and closes to prevent passage of fluid from the chamber. The liquid, which drains in the lumen past the passageway, refluxes into the passageway responsive to a positive pressure condition in the lumen relative to the pressure in the chamber, and the refluxing liquid flow forces air from the passageway into the chamber to close the valve. Air is confined in the chamber by the closed valve, and the liquid flow compresses the confined air in the chamber to develop a resistive pressure in the chamber which prevents the liquid from entering the chamber and contacting the valve.

United States Patent 1191 Binard 'et al.

VENT FOR LIQUID DRAINAGE SYSTEM .[75] Inventors: William J. Binard; JohnF. Dye,

both of Barrington, Ill.

[73] Assignee: The Kendall Company, Boston,

Mass.

221 Filed: June 2, 1971 21 Appl. No.: 149,315

[52] US. Cl "137/217, 128/349 R, 285/197,

285/197, 287, 423; DIG. l6, DIG. 22'

References Cited UNITED STATES PATENTS 3,419,009 12/1968 Ericson..l37/217 X 3,429,314 2/1969 Ericson ..128/349 R 2,690,744 10/1954 7Wallace 128/6 2,955,595 10/1960 Semple 137/318 X l 'I, II

[ May 1,1973

FOREIGN PATENTS OR APPLICATIONS 1,026,000 4/1966 Great Britain ..285/197Primary Examiner-Henry T. Klinksiek Attorney-Robert D. Chodera [5 7]ABSTRACT A vent for a liquid drainage system having a drainage lumen,including an air chamber, a one-way valve connected to the chamber, anda passageway connected between the chamber and drainage lumen. The valveopens to permit the passage of air into the drainage lumen, and closesto prevent passage of fluid from the chamber. The liquid, which drainsin the lumen past the passageway, refluxes into the passagewayresponsive to a positive pressure condition in the lumen relative to thepressure in the chamber, and the refluxing liquid flow forces air fromthe passageway into the chamber to close the valve. Air is confined inthe chamber by the closed valve, and the liquid flow compresses theconfined air in the chamber to develop a resistive pressure in thechamber which prevents the liquid from entering the chamber andcontacting the valve.

24 Claims, 13 Drawing Figures Paten tecl May 1, 1973 2 Sheets-Sheet 1Patented May 1, 1973 3,730,209

2 Sheets-Sheet 2 7 1 VENT FOR LIQUID DRAINAGE SYSTEM BACKGROUND OF THEINVENTION 1. Field of the Invention This invention relates to liquiddrainage systems, and more particularly to a protective device for avalve and filter in a drainage vent.

2. Description of the Prior Art It is known that in systems for thedrainage of fluids from the body, such as indwelling catheters, anegative pressure may be created in such systems which has a deleteriouseffect on the body. To alleviate this result, Ericson US. Pat. No.3,429,314 discloses a vented drainage system which prevents buildup of anegative pressure, and shows a filter unit positioned in the vent toprevent the passage of bacteria into the system. However, if fluids inthe system contact the filter unit, it may be rendered inoperable, andEricson US. Pat. No. 3,419,009 teaches the use of a valve to protect thefilter.

Andersen US. Pat. No. 3,1 l4,373 relates to a gastrointestinal sump tubeassembly having an adapter tube which may draw in ambient air, .andcheck valves in urinal collection bags are disclosed in Evans U.S. Pat.No. 2,883,985 and the British Pat. No. l,l28,l86. Reiss et al. US Pat.No. 3,526,218 shows a closed end manometer having a passageway ofcapillary dimension and a chamber to measure fluid pressures.

Although vented drainage systems, such as proposed by Ericson US Pat.No. 3,419,009, sustain the lifetime of the vent filter, it has beendetermined that where liquid refluxes against the vent valve theoperability of the system maybe impaired. For example, if the liquid,such as urine, contacts the valve while itis open, the liquid may enterthe valve and possibly contact the filter. In the course of time, thisliquid results in a buildup of deposits in the valve, and significantlydegrades its operability. Once the valve is functioning improperly,liquid may pass through the valve and the filter is damaged.

It is also desirable to prevent contact of the valve by the liquid whenit is closed, since the liquid remaining on the valve may subsequentlyimpair its operability.

SUMMARY OF THE INVENTION A principle feature of the present invention isthe provision ofa vent for a liquid drainage system which preventscontact of a one-way valve in the vent by the drainage liquid, thusincreasing the operable lifetime of the vent and system.

The vent of the present invention has the valve secured to an airchamber, and includes a passageway having one end connected to a lumenin the drainage system and the other end connected to the chamber. Thevalve opens to permit the passage of air into the chamber and lumen forventing, and closes to prevent passage of air from the chamber. Thefluid, which drains in the lumen past the passageway, refluxes into thepassageway responsive to a positive pressure condition in the lumen, andthe refluxing liquid flow forces air from the passageway into thechamber to close the valve. Air is confined in the chamber by the closedvalve, and the liquid flow compresses the confined air to develop aresistive pressure in the chamber.

A feature of the present invention is that the passageway hassufficiently small dimensions to permit only meniscal flow of the liquidtherein and prevent the break up of a liquid column in the passageway.

Another feature of the invention is that the drainage system is operableindependent of position of the vent.

A further feature of the invention is that the developed resistivepressure prevents the liquid from entering the chamber and contactingthe valve.

Yet another feature of the invention is that the volume of thepassageway relative to the volume of the chamber is sufficient fordevelopment of a resistive pressure which prevents flow of the liquidinto the chamber.

Still another feature of the invention is that the vent may be removablyattachable to the outside of a wall enclosing a fluid cavity.

Further features will become more fully apparent in the followingdescription of the embodiment of this invention and from: theappendedclaims.

DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a fragmentary perspective view, partly in section and partlybroken away, of the liquid drainage system and the ventjof the presentinvention;

FIG. 2 is a fragmentary longitudinal section view of the vent of FIG. 1;

FIG. 3 is a sectional view taken substantially as indicated along theline 33 of FIG. 2;

FIG. 4 is a fragmentary longitudinal sectional view of anotherembodiment of the invention;

FIGS. 5A, 5B and 5C are fragmentary perspective views, partly in sectionor partly broken away, of alternate embodiments of the invention;

FIG. 6 is a perspective view, partly in section and partly broken away,of a movable vent of the present invention;

FIGS. 7 and 8 are fragmentary perspective views showing attachment ofthe movable vent of FIG. 6 to the wall of a tube;

FIG. 9 is a fragmentary sectional view on an enlarged scale, showing theneedle and shroud of the movable vent prior to attachment;

FIG. 10 is a fragmentary sectional view on an enlarged scale, showingthe needle and shroud of the movable vent during attachment; t

FIG. 11 is a fragmentary perspective view, taken partly in section, ofanother embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Although the vent of theinvention is first described in a connection with an adapter for acatheter and liquid drainage tube in a urinary drainage system, it isunderstood that the invention has a broader scope, and may be includedin various types ofdrainage systems. Additionally, the invention may beincorporated in the catheter or drainage tube itself.

Referring now to FIGS. 1-3, a liquid drainage system, generallydesignated 20, is shown including an adapter, generally designated 22,having one end 24 received in the proximal end 26 of a catheter 28 and asecond end 30 which may be connected to a liquid drainage tube 32. Thecatheter 28 has a drainage lumen 34 extending from a drainage eye 35adjacent its distal end 36 to the proximal catheter end 26, and theadapter 22 has a drainage lumen 38 extending between its ends 24 and 30.When the catheter is inserted into the body of a patient, liquid drainsfrom the eye 35 to the tube 32 through the lumens 34 and 38.

The adapter 22 includes a vent, generally designated 40, for venting thedrainage lumen 38. The vent 40 has an air chamber 42 and a passageway orchannel means 44 having one end 46 connected to the lumen 38 and theother end 48 connected to the air or compression chamber 42. Thepassageway or venting channel 44 has sufficiently small cross-sectionaldimensions to permit only meniscal flow of the liquid in the passageway,and the chamber 42 is preferably elongated and generally aligned withthe lumen 38 for compactness of the adapter. The vent 40 also has aone-way air valve 50 located in the air chamber 42 and having one end 51open to the atmosphere and connected to one end 52 of the chamber 42. Abacterial filter 54 is connected to the valve end 51 to preventcontamination of the drainage system due to air passing through thevalve to the lumen 38.

In a preferred embodiment, the valve 50 is a flap valve and has an airinlet 55 positioned adjacent the other end of the chamber 56. However,it is contemplated that other one-way valves, such as ball or checkvalves, may be utilized in the vent 40. The flap valve 50 opens topermit passage of air into the chamber 42 for venting the lumen 38, withthe direction of air flow being indicated by the arrows in the drawings,and closes to prevent the passage of fluid from the chamber into thevalve and against the filter 54. Thus, the air valve or valve means 50controls the passage of fluid between the atmosphere and the lumen 38.

During normal operation of the drainage system 20, and particularly whena negative pressure exists in the lumen 38, liquid drains in the lumenpast the passageway or venting channel 44, and the lumen is vented tothe atmosphere through the valve 50. Thus, any negative pressure in thelumen is relieved by the vent, and possible suction injury to thepatients body is avoided. Since the valve 50 is removed from the lumen38 and air passes through the passageway 44 for venting, the drainageliquid does not contact the valve 50 during venting of the lumen.

However, occasionally a positive pressure, relative to the pressure inthe chamber 42, may build up in the lumen, and liquid refluxes from thelumen 38 into the passageway 44 responsive to the pressurized condition.The passageway has sufficiently small dimensions such that the refluxingliquid forms a meniscus in the passageway which prevents the flowingliquid from breaking up, irrespective of the position of the vent 50 andpassageway relative to the vertical. The meniscal flow forms a column ofliquid in the passageway which forces air from the passageway into thechamber 42, and the valve is closed prior to contact by the liquid dueto compression of air within the chamber. Accordingly, the liquid isprevented from passing into the open valve, and the chamber and meniscalforming passageway serve as means for closing the valve responsive tothe flow ofliquid into the passageway.

It is also desirable to prevent liquid from entering the chamber 42 atany time, since liquid in the chamber may enter the valve when it opens.Once the valve is closed and if the pressurized condition persists, theliquid column continues flowing in the passageway and forcing air fromthe passageway into the chamber. Since the air is confined in thechamber by the closed valve, the air is compressed and a resistivepressure to the flowing liquid is developed, with the compressed airacting as an air spring against the liquid column. Thus, the chamber,the closed valve or valve means, and the meniscal forming passagewayserve as means responsive to the liquid flow for developing a resistivepressure to impede the flow of liquid into the passageway.

In order to protect the valve and filter from damage or contamination bythe liquid, this principle is utilized to prevent the liquid fromentering the chamber. The amount of resistive pressure developed in thechamber is dependent on: (l) the volume of the passageway, since thisdetermines the amount of air which is forced into the chamber for apredetermined length of the liquid column, and (2) the volume of airspace in the chamber. Accordingly, for a given pressure in the lumen, apassageway may be selected which has a sufficiently large volumerelative to the volume of the chamber, in order for the compressing airto develop a pressure at least as large as the pressure of the liquidflow and prevent entry of the liquid into the chamber.

To achieve this result, preferably a relatively small chamber 42 ischosen for fast response of the valve in closing. Next, the possiblerange of positive pressures in the lumen is determined, and a passagewayis selected which has a sufficiently large volume to prevent liquid fromentering the chamber at the largest possible pressure in the range.However, the passageway is limited in width since it has meniscalforming dimensions, and the necessary volume may be attained byselecting the appropriate passageway length. To obtain the necessarylength, the passageway may define a tortuous path between the lumen andchamber, such as by winding it around the chamber. In the adapter 22,the passageway is lengthened by including a mid-portion which, as wellas the elongated chamber 42, is generally aligned with the lineardrainage channel 38.

The relative volume of the channel 44 and chamber 42 which is necessaryto prevent passage of liquid into the chamber may be derived as follows:Let,

P the pressure of the air in the channel and chamber prior to entry ofliquid into the channel, or approximately atmospheric pressure;

P the largest expected pressure in the channel and chamber of theconfined air, which is also the largest expected pressure in thedrainage lumen;

V the total volume of the chamber;

V, the volume of the chamber at the pressure P;

V the volume of the channel with no liquid in the channel;

V the volume of the air in the channel at the pressure P; and

K V /V or a parameter such that O K 1.

Now, according to Boyles law, and assuming a con stant temperature,

Since the volume of the passageway is selected such that the liquid doesnot enter the chamber, V V,,

I and,

Thus, the relative volume of the passageway and chamber is,

Hence, once the volume of the chamber V is selected, the range ofpressure differences (P-P) is known, and a desired ratio of V /V ischosen to determine how far the liquid should flow in the channel, thenecessary minimum volume for the channel V can be calculated by theexpression,

' valve. In the drainage system 20, the pressure difference (P'P) mayhave an approximate range of values of 100 cm of water, or from 1034 cmof water, atmospheric pressure, to l 134 cm of water.

Although an expression has been given above for the volume of thechannel V this calculation determines only the minimum measurement ofvolume necessary to insure containment of the liquid within thepassageway 44. Thus, the passageway 44 may have a greater volume andlength than indicated by the expression, as there is no upper bound onthe volume of the meniscal forming passageway. Also, it is contemplatedthat with a sufficiently small valve 50, the chamber 42 may be acontinuation of the passageway 44 with their separation beingindistinguishable.

Another embodiment of the invention is illustrated in FIG. 4, in whichthe vent 40 is secured to a liquid drainage system 20, such as a liquiddrainage tube or an adapter for connecting a drainage tube to acatheter. The vent 40 has an outer wall 60 which surrounds a cavity 62,and the filter 54'and the valve 50 are connected to one end 64 of thewall 60. An inner wall 66 defines the passageway 44 which extends intothe cavity 62, and separates the passageway from the chamber 42 in thecavity 62. Air passes through the valve inlet 55 into a blind pouch ofthe chamber 42, and from the pouch it entersthe outer end of thepassageway 44 and passes into the lumen 38.

Alternate embodiments of the invention are shown in FIGS. A, 5B and 5C,with the chambers 42 in these vents having different shapes toillustrate that the chamber may be shaped in any suitable manner, andwith the passageways 44 having no maximum limit on their lengths. InFIGS. 5B and 5C the valve 50 is removed from the passageway byconnecting the valve to one end of the chamber and connecting thepassageway to the other end of the chamber. As shown in FIG. 5A, the onepassageway end 46 is connected to the lumen 38, and the remote end ofthe passageway 48 extends into the chamber 42, thus increasing thelength and volume of the passageway. Although the passageway extensionis shown as integral with the chamber wall, alternatively, a separatetube may be utilized to extend the passageway. In FIG. 5C, a tube isconnected to the valve 50, and liquid passes from a fluid or liquidsource (not shown) through the tube 70 and valve 50 into the channel 38,with the valve controlling the passage of fluid between the source andthe channel. In FIGS. 5A and 5B, the source of fluid is the atmosphereor a gas.

Referring to FIGS. 6-10, a movable vent, generally designated 90, isshown having a case 92 which is removably attachable to the drainagesystem 20. In a preferred embodiment, the case 92 is attached to theoutside of the wall 94 of a liquid drainage tube 96 in the system 20 tovent the tube lumen or cavity 38. However, it is understood that by asuitable choice of the attaching means, the case may be utilized forother types of fluid cavities by. attaching the case to a wall which atleast partially encloses the fluid cavity.

As shown in FIG. 6, the vent case 92 has an air chamber 42, a valve 50,and a filter 54, as previously described. As illustrated in FIGS. 6, 9and 10, a connecting needle, generally designated 98, for penetratingthe tube wall 94, has a base portion 100 secured to the case 92 and atip 102 extending outwardly from the case. The needlehas an internalmeniscal forming passageway 104 extending from the base portion 100 toan external opening 106 in the needle adjacent the tip 102, but thepassageway may terminate at the tip 102 itself, if desired.

The needle 98 has a sufficient length for the needle to penetrate thetube wall 94 and position the needle opening 106 in the lumen 38, and,preferably, the wall 94 of the tube 96 is sufficiently elastic such thatthe needle 98 may puncture the wall during attachment of the case 92.However, the vent may be attached to a relatively rigid wall, with anopening first being formed in the wall by other suitable means, such asby drilling, and the needle or needle means may then be inserted throughthe opening.

In order to lengthen the passageway 104, the case 92 has a tube 108connected to the needle base portion 100 and extending into the chamber42. The tube 108 has a lumen or passageway 110 connected to the needlepassageway 104. When the case .92 is attached to the tube 96, the needlepassageway 104 and tube lumen 110 define a channel communicating betweenthe cavity 38 and chamber 42, with this channel having meniscal formingdimensions for operation like the passageway 44, as previouslydescribed. Thus, the nee-.

dle 98 and the tube 108 serve as means for fluidly connecting thechannel 38 and the chamber 42. During venting of the channel 38, airpasses through the connecting means from the chamber to the channel 38,and fluid flows from the channel into the connecting means responsive toa pressurized condition in the channel to force air from the passageways104 and 110 into the chamber 42 and close the valve 50.

As best illustrated in FIG. 9, a hollow flexible shroud 114 surrounds alongitudinal portion of the needle 98. The shroud 114 has one end 116secured to the needle base portion 100 and a free end 118 which extendstoward the needle tip 102. In a preferred embodiment, the shroud 114 hasa sufficient length for the free end 118 to cover the needle opening 106prior to attachment of the case. Accordingly, the shroud 114 closes theneedle opening 106 when the vent is not in use, and protects thepassageway 104 from contamination.

As shown in FIG. 10, during attachment of the vent the needle puncturesa hole 120 in the wall 94, and the shroud 114 flexes toward the needlebase portion 100 to seal the punctured opening 120 and prevent leakage.If desired, the attached vent may be removed from the tube 96, and theopening 120 is sealed by suitable means to continue operation of thedrainage system 20.

As illustrated in FIG. 6,.the case 92 has a plurality of opposed legs124 extending outwardly from the case 92 to frictionally engage theoutside of the wall 94 and attach the vent 90 to the tube 96. Theopposed legs 124 are concave and aligned in pairs and may be resilientto grippingly receive the tubular wall. However, it is also contemplatedthat the legs 124 may be bendable for clamping the legs around theoutside of the wall. As shown in FIGS. 7 and 8, the vent 90 is attachedby pressing the case 92 against the tube 96 to puncture the wall 94 andengage the legs 124, and the legs thus serve as means for removablyattaching the case 92 to the tube 96.

A similar embodiment is shown in FIG. 11, in which the case- 92 isremoved from the needle 98. The vent 90 has means for penetrating thetube wall 94, generally designated 126, which includes the needle 98 andthe needle passageway 104 having one end terminating in an opening (notshown) adjacent the needle tip. The penetrating means 126 also has aplurality of legs 124 extending outwardly from a plate 128 to releasablyretain the penetrating means to the tube 96, as discussed above. A tube130 has one end 132 connected to the penetrating means 126 and the otherend 134 connected to the case 92, and the tube 130 has a meniscalforming lumen 136 which communicates between the' other end of thepassageway104 and the inside of the chamber 42. Thus, the tube 130serves to lengthen the meniscal forming passageway and increase itsvolume, and if the environment in the area of the tube 96 is subject towetting, the filter 54 is removed from the tube for protection.

The foregoing detailed description is given for clearness ofunderstanding only, and no unnecessary limitations should be understoodtherefrom, as modifications will be obvious to those skilled in the art.

We claim:

1. In a liquid drainage system having a liquid drainage lumen, a ventfrom the atmosphere for said lumen comprising:

an air chamber;

a one-way valve operatively connected to said chamber, said valveopening to permit the passage of air into the chamber and closing toprevent the passage of fluid from the chamber;

a channel fluidly connecting said chamber and lumen permitting thepassage of air from the chamber to the lumen for venting the lumen withsaid liquid draining past the channel, said liquid refluxing from thelumen into the channel responsive to a positive pressure condition inthe lumen relative to the pressure in the chamber, with said channelhaving sufficiently small dimensions to permit only meniscal flow of therefluxing liquid therein, and with the refluxing liquid forcing air fromthe channel into the chamber to close said valve prior to contact of thevalve by the liquid; and

a filter communicating with the valve remote the air chamber.

2. The vent of claim 1 wherein air is confined in the chamber by theclosed valve, and said liquid flow compresses confined air in thechamber to develop a resistive pressure in the chamber for impeding saidliquid flow in the channel.

3. The vent of claim 2 wherein the volume of the channel relative to thevolume of the chamber is sufficient for the flowing liquid to develop aresistive pressure at least as large as the pressure of the liquid flowto prevent entry of the liquid into the chamber.

4. The vent of claim 3 wherein the volumes of the channel and chamber Vand V respectively, are ap' proximately related by the expression:

where,

P is the pressure of the air in the channel and chamber prior to entryof liquid into the channel;

P is the largest expected pressure in the channel and chamber of theconfined air; and

K is a selected parameter, such that O K 1.

5. The vent of claim 4 wherein the pressure P is atmospheric pressure.

6. The vent of claim 4 wherein the pressure difference (PP) has a valuewhich ranges between 0 and cm of water.

7. The vent of claim 4 wherein the parameter K= V /V,, and V is thevolume of confined air in the passageway at the largest pressure P.

8. The vent of claim 1 wherein said vent channel has one end connectedto the drainage lumen and a remote end connected to the air chamber,said channel defining a tortuous path between the drainage lumen and thechamber.

9. The vent of claim 1 wherein said channel has one end connected to thedrainage lumen and a remote end connected to the air chamber, saiddrainage lumen includes a generally linear portion in the region of saidone channel end, and at least a portion of the channel is generallyaligned with said linear lumen portion.

10. The vent of claim 1 wherein said vent channel comprises, apassageway having one end connected to the drainage lumen and a remoteend extending into said air chamber.

11. A vent for a liquid cavity which is at least partially enclosed by awall, comprising:

a case having an air chamber;

a one-way valve operatively connected to said air chamber forcontrolling the passage of air into the chamber;

means for removably attaching said case to the outside of said wallrelative to the cavity; and

means fluidly connecting the cavity with the chamber of the attachedcase, said connecting means including a passageway for the passage ofair from the chamber to the cavity for venting the cavity, with saidliquid flowing from the cavity into the passageway responsive to apositive pressure condition in the cavity relative to the pressure inthe chamber, and with said passageway having sufficiently smalldimensions to permit only meniscal flow of the liquid therein, wherebythe liquid forces air from the passageway into the chamber to close saidvalve prior to contact of the valve by the liquid.

12. The vent of claim 11 wherein said wall has a tubular shape with thefluid cavity being defined by a lumen in the tubular wall, and saidattaching means comprises, a plurality of spaced legs extendingoutwardly from the vent case, said legs being opposed to frictionallyengage the outside of the wall for attachment of the vent.

13. The vent of claim 12 wherein said opposed legs are aligned in pairs,said legs are resilient and concave to grippingly receive the tubularwall, and said attaching means includes a plurality of said leg pairs.

14. The vent of claim 12 wherein said opposed legs are bendable forclamping the case legs around the outside of the tubular wall.

15. The vent of claim 11 wherein said connecting means includes, meansfor puncturing the cavity wall during attachment of the case.

16. The vent of claim 11 wherein said connecting means penetrates thecavity wall through an opening in the wall, and including means forsealing said wall opening upon attachment of the case to preventleakage.

17. The vent of claim 11 wherein said connecting means comprises, aneedle having a base portion and a tip respectively secured to andextending outwardly from said case, said needle having a passagewayextending from the base portion to an external opening in the needleadjacent said tip, and said needle having a sufficient length topenetrate the wall and position the needle opening in said cavity uponattachment of the case for connecting the cavity and chamber. w 5 18.The vent of claim 17 including a hollow flexible shroud surrounding atleast a longitudinal portion of the needle, said shroud having one endsecured adjacent the base portion of the needle and a free end extending toward the needle tip prior to attachment of the case, said freeshroud end flexing toward the needle base portion during attachment ofthe case to seal the wall adjacent the puncture.

19. The vent of claim 18 wherein said shroud covers the needle openingprior to attachment of the case.

20. The vent of claim 11 wherein said connecting means includes achannel communicating between the cavity and chamber after attachment ofthe case, said channel having sufficiently small dimensions to permitonly meniscal flow of the fluid therein.

21. The vent of claim 20 including a tube extending into said chamberand having a lumen defining a portion of said channel.

22. The vent of claim 11 including a filter connected to said valveremote the chamber.

23. A vent for a fluid cavity which is at least partially enclosed by awall, com rising:

a case having an air c amber;

a one-way valve operatively connected to said air chamber forcontrolling the passage of air into the chamber;

means for penetrating the cavity wall, including a passageway having oneend communicating with the cavity after penetration; and

a tube having one end connected to the penetrating means and the otherend connected to said case, said tube having a lumen communicatingbetween the other end of said passageway and the inside of the chamber.V

24. The vent of claim 23 including means releasably 40 retaining thepenetrating means in the cavity wall.

1. In a liquid drainage system having a liquid drainage lumen, a ventfrom the atmosphere for said lumen comprising: an air chamber; a one-wayvalve operatively connected to said chamber, said valve opening topermit the passage of air into the chamber and closing to prevent thepassage of fluid from the chamber; a channel fluidly connecting saidchamber and lumEn permitting the passage of air from the chamber to thelumen for venting the lumen with said liquid draining past the channel,said liquid refluxing from the lumen into the channel responsive to apositive pressure condition in the lumen relative to the pressure in thechamber, with said channel having sufficiently small dimensions topermit only meniscal flow of the refluxing liquid therein, and with therefluxing liquid forcing air from the channel into the chamber to closesaid valve prior to contact of the valve by the liquid; and a filtercommunicating with the valve remote the air chamber.
 2. The vent ofclaim 1 wherein air is confined in the chamber by the closed valve, andsaid liquid flow compresses confined air in the chamber to develop aresistive pressure in the chamber for impeding said liquid flow in thechannel.
 3. The vent of claim 2 wherein the volume of the channelrelative to the volume of the chamber is sufficient for the flowingliquid to develop a resistive pressure at least as large as the pressureof the liquid flow to prevent entry of the liquid into the chamber. 4.The vent of claim 3 wherein the volumes of the channel and chamber V2and V1, respectively, are approximately related by the expression: V2/V1(P''-P)/(P-KP''), where, P is the pressure of the air in the channel andchamber prior to entry of liquid into the channel; P'' is the largestexpected pressure in the channel and chamber of the confined air; and Kis a selected parameter, such that O<K<1.
 5. The vent of claim 4 whereinthe pressure P is atmospheric pressure.
 6. The vent of claim 4 whereinthe pressure difference (P''-P) has a value which ranges between 0 and100 cm of water.
 7. The vent of claim 4 wherein the parameter K V2''/V1,and V2'' is the volume of confined air in the passageway at the largestpressure P''.
 8. The vent of claim 1 wherein said vent channel has oneend connected to the drainage lumen and a remote end connected to theair chamber, said channel defining a tortuous path between the drainagelumen and the chamber.
 9. The vent of claim 1 wherein said channel hasone end connected to the drainage lumen and a remote end connected tothe air chamber, said drainage lumen includes a generally linear portionin the region of said one channel end, and at least a portion of thechannel is generally aligned with said linear lumen portion.
 10. Thevent of claim 1 wherein said vent channel comprises, a passageway havingone end connected to the drainage lumen and a remote end extending intosaid air chamber.
 11. A vent for a liquid cavity which is at leastpartially enclosed by a wall, comprising: a case having an air chamber;a one-way valve operatively connected to said air chamber forcontrolling the passage of air into the chamber; means for removablyattaching said case to the outside of said wall relative to the cavity;and means fluidly connecting the cavity with the chamber of the attachedcase, said connecting means including a passageway for the passage ofair from the chamber to the cavity for venting the cavity, with saidliquid flowing from the cavity into the passageway responsive to apositive pressure condition in the cavity relative to the pressure inthe chamber, and with said passageway having sufficiently smalldimensions to permit only meniscal flow of the liquid therein, wherebythe liquid forces air from the passageway into the chamber to close saidvalve prior to contact of the valve by the liquid.
 12. The vent of claim11 wherein said wall has a tubular shape with the fluid cavity beingdefined by a lumen in the tubular wall, and said attaching meanscomprises, a plurality of spaced legs extending outwardly from the ventcase, said legs being opposed to frictionally engage the outside of thewall for attachment of the vent.
 13. The vent of claim 12 wherein saidopposed legs are aligned in pairs, said legs are resilient and concaveto grippingly receive the tubular wall, and said attaching meansincludes a plurality of said leg pairs.
 14. The vent of claim 12 whereinsaid opposed legs are bendable for clamping the case legs around theoutside of the tubular wall.
 15. The vent of claim 11 wherein saidconnecting means includes, means for puncturing the cavity wall duringattachment of the case.
 16. The vent of claim 11 wherein said connectingmeans penetrates the cavity wall through an opening in the wall, andincluding means for sealing said wall opening upon attachment of thecase to prevent leakage.
 17. The vent of claim 11 wherein saidconnecting means comprises, a needle having a base portion and a tiprespectively secured to and extending outwardly from said case, saidneedle having a passageway extending from the base portion to anexternal opening in the needle adjacent said tip, and said needle havinga sufficient length to penetrate the wall and position the needleopening in said cavity upon attachment of the case for connecting thecavity and chamber.
 18. The vent of claim 17 including a hollow flexibleshroud surrounding at least a longitudinal portion of the needle, saidshroud having one end secured adjacent the base portion of the needleand a free end extending toward the needle tip prior to attachment ofthe case, said free shroud end flexing toward the needle base portionduring attachment of the case to seal the wall adjacent the puncture.19. The vent of claim 18 wherein said shroud covers the needle openingprior to attachment of the case.
 20. The vent of claim 11 wherein saidconnecting means includes a channel communicating between the cavity andchamber after attachment of the case, said channel having sufficientlysmall dimensions to permit only meniscal flow of the fluid therein. 21.The vent of claim 20 including a tube extending into said chamber andhaving a lumen defining a portion of said channel.
 22. The vent of claim11 including a filter connected to said valve remote the chamber.
 23. Avent for a fluid cavity which is at least partially enclosed by a wall,comprising: a case having an air chamber; a one-way valve operativelyconnected to said air chamber for controlling the passage of air intothe chamber; means for penetrating the cavity wall, including apassageway having one end communicating with the cavity afterpenetration; and a tube having one end connected to the penetratingmeans and the other end connected to said case, said tube having a lumencommunicating between the other end of said passageway and the inside ofthe chamber.
 24. The vent of claim 23 including means releasablyretaining the penetrating means in the cavity wall.